Light emitting device

ABSTRACT

A light emitting diode package includes: a housing; a light emitting diode chip arranged in the housing; a wavelength conversion unit arranged on the light emitting diode chip; a first fluorescent substance distributed inside the wavelength conversion unit and emitting light having a peak wavelength in the cyan wavelength band; and a second fluorescent substance distributed inside the wavelength conversion unit and emitting light having a peak wavelength in the red wavelength band, wherein the peak wavelength of light emitted from the light emitting diode chip is located within a range of 415 nm to 430 nm.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. patent application Ser. No.15/518,170, filed Apr. 10, 2017, which is the National Stage Entry ofInternational Application No. PCT/KR2015/010590, filed on Oct. 7, 2015,and claims priority from Korean Patent Application No. 10-2014-0136095,filed on Oct. 8, 2014, and Koran Patent Application No. 10-2015-0008212,filed on Jan. 16, 2015, and Korean Patent Application No.10-2015-0008213, filed on Jan. 16, 2015, each of which are incorporatedherein by reference for all purposes as if fully set forth herein.

BACKGROUND Field

Exemplary embodiments of the present disclosure relate to a lightemitting device. More particularly, exemplary embodiments of the presentdisclosure relate to a light emitting device which has improvedproperties in terms of reliability, color rendition, and luminousintensity.

Discussion of the Background

A light emitting diode (LED) package is a compound semiconductor havinga semiconductor p-n junction and emits light through recombination ofminority carriers (electrons or holes). A light emitting deviceincluding light emitting diodes has low power consumption and long lifespan and can be miniaturized.

A light emitting device can realize white light using a phosphor whichis a wavelength conversion means. That is, white light can be realizedby placing a phosphor on a light emitting diode chip such that afraction of light primarily emitted from a light emitting diode chip canbe mixed with wavelength-converted light secondarily emitted from thephosphor. Such white light emitting devices are cheap and simple inprinciple and structure and thus are widely used.

Specifically, white light may be obtained by applying a phosphor capableof emitting yellow-green or yellow light by absorbing a fraction of bluelight as excitation light on a blue light emitting diode chip. KoreanPatent Publication No. 10-2004-0032456 discloses a light emitting diodewhich includes a blue light emitting diode chip and phosphors attachedto the blue light emitting diode chip and emitting yellow-green oryellow light using a fraction of light as an excitation source, therebyemitting white light through combination of the blue light from thelight emitting diode with the yellow-green or yellow light from thephosphors.

However, since such a white light emitting device utilizes emission ofyellow phosphors, light from the light emitting device has a spectrumoutside the green and red regions, thereby causing reduction in colorrendition. In particular, when used as a backlight unit, the white lightemitting device has difficulty in realizing a color close to a naturalcolor due to low color purity of light having passed through a colorfilter.

In order to overcome these problems, there has been proposed a lightemitting diode fabricated using a blue light emitting diode chip andphosphors emitting blue light and green light using blue light asexcitation light. Such a light emitting diode can realize white lighthaving high color rendition by mixing the green light and red light fromthe phosphors excited by the blue light. When such a white lightemitting diode is used as a backlight unit, light from the white lightemitting diode can have relatively high color purity even after passagethrough a color filter, thereby realizing images closer to naturalcolors. However, the light emitting diode using the blue light emittingdiode chip has relatively high intensity of blue light and thus cancause various side effects to the human body, such as sleep disorders,when used as illumination. For example, use of the light emitting diodecan cause inhibition of melatonin, thereby affecting sleep patterns. Forexample, there is a high possibility that sleep disorders may occur.

In order to realize white light, an ultraviolet light emitting diodechip may be used instead of a blue light emitting diode chip. A lightemitting device using an ultraviolet light emitting diode chip canrealize high color rendition, allows easy conversion of the colortemperature according to combination of phosphors, and can haveexcellent yield. However, the ultraviolet light emitting diode chipemits light at a wavelength having relatively high energy and thus cancause degradation or cracking of an encapsulant and discoloration of aplated lead frame. Thus, the light emitting device using the ultravioletlight emitting diode chip can exhibit poor reliability.

Therefore, there is a need for a light emitting device which canovercome the above problems.

R9 is an indicator of strong redness, which is important in areasrelated to skin color, artwork, clothing, and food. For a light emittingdevice using a light emitting diode chip emitting near-violet light, aCASN phosphor having a long peak wavelength is used to provide a CRI of90 or higher and an R9 of 50 or higher. However, when using a CASN-basedlong wavelength phosphor, there is a problem in that a light emittingdevice can be reduced in luminous intensity by 4% or more despite havingincreased R9.

SUMMARY

Exemplary embodiments of the present disclosure provide a light emittingdevice which has improved reliability and color rendition.

Exemplary embodiments of the present disclosure provide a light emittingdevice which has improved luminous efficacy and luminous intensity.

Exemplary embodiments of the present disclosure provide a light emittingdevice which has increased CRI and R9 values.

In accordance with one aspect of the present disclosure, a lightemitting device includes: a housing; a light emitting diode chipdisposed in the housing; a wavelength converter disposed on the lightemitting diode chip; a first phosphor distributed in the wavelengthconverter and emitting light having a peak wavelength in the cyanwavelength band; and a second phosphor distributed in the wavelengthconverter and emitting light having a peak wavelength in the redwavelength band, wherein light emitted from the light emitting diodechip has a peak wavelength of 415 nm to 430 nm.

The first phosphor may include at least one of LuAG, YAG, nitride, andsilicate phosphors.

The second phosphor may include at least one of CASN, CASON, and SCASNphosphors.

The light emitted from the first phosphor may have a peak wavelength of500 nm to 540 nm and the light emitted from the second phosphor may havea peak wavelength of 600 nm to 650 nm.

The light emitting device may further include: a third phosphordistributed in the wavelength converter and emitting light having a peakwavelength in the blue wavelength band, wherein the third phosphor mayinclude at least one of SBCA, BAM, silicate, and nitride phosphors.

The light emitted from the third phosphor may have a peak wavelength of450 nm to 480 nm.

The light emitting device may emit white light generated by combinationof light from the light emitting diode chip with light from the firstphosphor and light from the second phosphor, wherein the white light mayhave a CRI of 85 or higher.

The wavelength converter may include at least one of silicone, epoxy,PMMA, PE, and PS.

The light emitting device may further include a buffer portion disposedbetween the wavelength converter and the light emitting diode chip,wherein the buffer portion may have lower hardness than the wavelengthconverter.

The wavelength converter may include: a first wavelength convertercovering the light emitting diode chip; and a second wavelengthconverter covering the first wavelength converter, wherein the firstwavelength converter may contain the second phosphor and the secondwavelength converter may contain the first phosphor.

The housing may include a reflector reflecting the light emitted fromthe light emitting diode chip.

The housing may further include a barrier reflector covering thereflector.

In accordance with another aspect of the present disclosure, a lightemitting device includes: a first phosphor excited by light from thelight emitting diode chip to emit light having a peak wavelength in thecyan wavelength band; and a second phosphor excited by light from thelight emitting diode chip to emit light having a peak wavelength in thered wavelength band, wherein the light emitted from the light emittingdiode chip has a peak wavelength of 415 nm to 430 nm; the light emittingdevice emits white light generated by combination of the light from thelight emitting diode chip with the light from the first phosphor and thelight from the second phosphor; and 40% or more of an optical spectrumof the white light is distributed in a wavelength range of 500 nm to 600nm.

The light emitted from the first phosphor may have a peak wavelength of500 nm to 540 nm and the light emitted from the second phosphor may havea peak wavelength of 600 nm to 650 nm.

The white light may have a CRI of 85 or higher.

The first phosphor may include at least one of LuAG, YAG, nitride, andsilicate phosphors.

The second phosphor may include at least one of CASN, CASON, and SCASNphosphors.

The light emitting device may further include: a third phosphor excitedby the light from the light emitting diode chip to emit light having apeak wavelength in the blue wavelength band, wherein the third phosphormay include at least one of SBCA, BAM, silicate, and nitride phosphors.

The light emitted from the third phosphor may have a peak wavelength of450 nm to 480 nm.

In accordance with a further aspect of the present disclosure, a whitelight emitting device includes: a light emitting diode emitting lighthaving a peak wavelength of 415 nm to 435 nm; and a wavelength converterdisposed on the light emitting diode, wherein the wavelength converterincludes: a first red phosphor and a second red phosphor each emittinglight having a peak wavelength in the red wavelength band; a greenphosphor emitting light having a peak wavelength in the green wavelengthband; and a cyan phosphor emitting light having a peak wavelength in thecyan wavelength band; the first red phosphor and the second red phosphorare formed of different materials; and light emitted from the lightemitting device has a CRI of 90 or higher. Thus, the white lightemitting device can have excellent properties in terms of colorrendition and luminous intensity.

The first red phosphor may include a phosphor represented by A₂MF₆:Mn,wherein A is any one of selected from the group consisting of Li, Na, K,Rb, Ce, and NH₄, and M is any one of selected from the group consistingof Si, Ti, Nb, and Ta.

The green phosphor may include a silicate phosphor.

The silicate phosphor may include a phosphor represented by(Ba,Sr,Ca)₂SiO₄:EU.

The second red phosphor may include a CASN phosphor.

The CASN phosphor may include a phosphor represented by (Sr,Ca)AlSiN₃:EUor CaAlSiN₃:EU.

The cyan phosphor may include an LuAG phosphor.

The LuAG phosphor may include a phosphor represented by Lu₃Al₅O₁₂:Ce orLu₃(Al,X)₅O₁₂:Ce (where X is a group III element other than Al, and Alis partially substituted with a group III element other than Al).

A weight ratio of the cyan phosphor to the green phosphor may be 8 to9.9:0.1 to 2 and a weight ratio of the second red phosphor to the firstred phosphor may be 2.5 to 5:7.5 to 5.

The first red phosphor and the second red phosphor may emit light havinga wavelength of 600 nm to 630 nm, the green phosphor may emit lighthaving a wavelength of 520 nm to 550 nm, and the cyan phosphor may emitlight having a wavelength of 490 nm to 550 nm.

The wavelength converter may cover at least part of the light emittingdiode.

In accordance with yet another embodiment of the present disclosure, awhite light emitting device includes: a light emitting diode emittinglight having a peak wavelength of 415 nm to 435 nm; and a wavelengthconverter disposed on the light emitting diode, wherein the wavelengthconverter includes: a first red phosphor represented by A₂MF₆:Mn; asecond red phosphor represented by (Sr,Ca)AlSiN₃:EU or CaAlSiN₃:EU; agreen phosphor represented by (Ba,Sr,Ca)₂SiO₄:EU; and a cyan phosphorrepresented by Lu₃Al₅O₁₂:Ce or Lu₃(Al,X)₅O₁₂:Ce (where Al is partiallyreplaced by a group III element other than Al), and a weight ratio ofthe cyan phosphor to the green phosphor is 8 to 9.9:0.1 to 2 and aweight ratio of the second red phosphor to the first red phosphor is 2.5to 5:7.5 to 5, (where A is any one selected from the group consisting ofLi, Na, K, Rb, Ce, and NH₄, M is any one selected from the groupconsisting of Si, Ti, Nb, and Ta, and X is a group III element otherthan Al). Thus, the white light emitting device can have excellentproperties in terms of color rendition and luminous intensity.

In accordance with yet another aspect of the present disclosure, a whitelight emitting device includes: a light emitting diode emitting lighthaving a peak wavelength of 415 nm to 435 nm; and a wavelength converterdisposed on the light emitting diode, wherein the wavelength converterincludes a red phosphor emitting light having a peak wavelength in thered wavelength band, a green phosphor emitting light having a peakwavelength in the green wavelength band, and a cyan phosphor emittinglight having a peak wavelength in the cyan wavelength band; the lightemitted from the light emitting device has a CRI of 90 or higher; andthe light emitting device has a luminous intensity variation rate ofhigher than 100%, as calculated according to Equation 1:

Luminous intensity variation rate (%)=(F ₁ /F ₀)×100.  [Equation 1]

F₁: Luminous intensity (unit: lm) of light emitted from the lightemitting device

F₀: luminous intensity (unit: lm) of light emitted from a light emittingdevice including a wavelength converter only including a CASN phosphorrepresented by (Sr,Ca)AlSiN₃:EU and an LuAG phosphor represented byLu₃Al₅O₁₂:Ce or Lu₃(Al,X)₅O₁₂:Ce (where X is a group III element otherthan Al, and Al is partially substituted with a group III element otherthan Al) as phosphors.

In accordance with yet another aspect of the present disclosure, a whitelight emitting device includes: a light emitting diode emitting lighthaving a peak wavelength of 415 nm to 435 nm; and a wavelength converterdisposed on the light emitting diode, wherein the wavelength converterincludes a first red phosphor and a second red phosphor each emittinglight having a peak wavelength in the red wavelength band and a cyanphosphor emitting light having a peak wavelength in the cyan wavelengthband; the first red phosphor and the second red phosphor are formed ofdifferent materials; and light emitted from the light emitting devicehas a CRI of 90 or higher and an R9 of 50 or higher. Thus, the whitelight emitting device can have excellent properties in terms of colorrendition and luminous intensity.

The first red phosphor may include a phosphor represented by A₂MF₆:Mn,wherein A is any one selected from the group consisting of Li, Na, K,Rb, Ce, and NH₄, and M is any one selected from the group consisting ofSi, Ti, Nb, and Ta.

The second red phosphor may include a CASN phosphor.

The CASN phosphor may include a phosphor represented by(Sr,Ca)AlSiN₃:EU.

The cyan phosphor may include an LuAG phosphor.

The LuAG phosphor may include a phosphor represented by Lu₃Al₅O₁₂:Ce orLu₃(Al,X)₅O₁₂:Ce (where X is a group III element other than Al, and Alis partially substituted with a group III element other than Al).

A weight ratio of the second red phosphor to the first red phosphor maybe 0.5 to 4:6.5 to 9.5. Thus, the white light emitting device can haveexcellent properties in terms of color rendition and luminous intensity.

The first red phosphor and the second red phosphor may emit light havinga wavelength of 600 nm to 660 nm and the cyan phosphor may emit lighthaving a wavelength of 490 nm to 550 nm.

The wavelength converter may cover at least part of the light emittingdiode.

In accordance with yet another aspect of the present disclosure, thereis provided a white light emitting device, including: a light emittingdiode emitting light having a peak wavelength of 415 nm to 435 nm; and awavelength converter disposed on the light emitting diode, wherein thewavelength converter comprises: a first red phosphor represented byA₂MF₆:Mn; a second red phosphor represented by (Sr,Ca)AlSiN₃:EU; and acyan phosphor represented by Lu₃Al₅O₁₂:Ce or Lu₃(Al,X)₅O₁₂:Ce (where Alis partially substituted with a group III element other than Al), and aweight ratio of the second red phosphor to the first red phosphor is 0.5to 4:6.5 to 9.5 (where A is any one selected from the group consistingof Li, Na, K, Rb, Ce, and NH₄, M is any one selected from the groupconsisting of Si, Ti, Nb, and Ta, and X is a group III element otherthan Al).

In accordance with yet another aspect of the present disclosure, a whitelight emitting device includes:

a light emitting diode emitting light having a peak wavelength of 415 nmto 435 nm; and

a wavelength converter disposed on the light emitting diode,

wherein the wavelength converter includes a red phosphor emitting lighthaving a peak wavelength in the red wavelength band and a cyan phosphoremitting light having a peak wavelength in the cyan wavelength band;

the light emitted from the light emitting device has a CRI of 90 orhigher and an R9 of 50 or higher; and

the light emitting device has a luminous intensity variation rate ofhigher than 98.8%, as calculated according to Equation 1:

Luminous intensity variation rate (%)=(F1/F0)×100.  [Equation 1]

F₁: Luminous intensity (unit: lm) of light emitted from the lightemitting device

F₀: luminous intensity (unit: lm) of light emitted from a light emittingdevice including a wavelength converter only including a CASN phosphorrepresented by (Sr,Ca)AlSiN₃:EU and an LuAG phosphor represented byLu₃Al₅O₁₂:Ce or Lu₃(Al,X)₅O₁₂:Ce (where X is a group III element otherthan Al, and Al is partially substituted with a group III element otherthan Al) as phosphors.

Exemplary embodiments of the present disclosure provide a light emittingdevice, which can emit light having an optical spectrum concentrated ina wavelength range having high luminous efficacy, thereby improvingluminous efficacy and luminous intensity. In addition, a light emittingdiode chip having a peak wavelength in the visible range is used in thelight emitting device, thereby improving reliability of the lightemitting device while enhancing color rendition of white light emittedfrom the light emitting device.

Exemplary embodiments of the present disclosure provide a light emittingdevice emitting light having high color rendition and high luminousintensity.

Exemplary embodiments of the present disclosure provide a light emittingdevice emitting light having high CRI and R9 values and high luminousintensity.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention, andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a schematic sectional view of a light emitting deviceaccording to one exemplary embodiment of the present disclosure.

FIG. 2 is a schematic sectional view of a light emitting deviceaccording to another exemplary embodiment of the present disclosure.

FIG. 3 is a schematic sectional view of a light emitting deviceaccording to a further exemplary embodiment of the present disclosure.

FIG. 4 is a schematic sectional view of a light emitting deviceaccording to yet another exemplary embodiment of the present disclosure.

FIG. 5 is a schematic sectional view of a light emitting deviceaccording to yet another exemplary embodiment of the present disclosure.

FIG. 6 is a schematic sectional view of a light emitting deviceaccording to yet another exemplary embodiment of the present disclosure.

FIG. 7 is a graph comparing optical spectra of a light emitting deviceaccording to the exemplary embodiment of the present disclosure and atypical light emitting device.

FIG. 8 is a schematic sectional view of a light emitting deviceaccording to yet another exemplary embodiment of the present disclosure.

FIG. 9 is a schematic sectional view of a light emitting deviceaccording to yet another exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Hereinafter, exemplary embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings. Itshould be understood that the present disclosure is not limited to thefollowing embodiments and may be embodied in different ways, and thatthe embodiments are provided for complete disclosure and thoroughunderstanding of the present disclosure by those skilled in the art. Inaddition, it should be noted that the drawings are not to precise scaleand may be exaggerated in thickness of lines or size of components fordescriptive convenience and clarity only. It will be understood thatwhen an element such as a layer, film, region or substrate is referredto as being placed “above (or below)” or “on (or under)” anotherelement, it can be directly placed on the other element, or interveninglayer(s) may also be present. Further, like components will be denotedby like reference numerals throughout the specification and theaccompanying drawings.

FIG. 1 is a schematic sectional view of a light emitting deviceaccording to one exemplary embodiment of the present disclosure.

Referring to FIG. 1, a light emitting device according to this exemplaryembodiment includes a housing 101, a light emitting diode chip 102, awavelength converter 104, a first phosphor 105, and a second phosphor106.

In this exemplary embodiment, the light emitting diode chip 102, thewavelength converter 104, the first phosphor 105, and the secondphosphor 106 may be disposed in the housing 101. The housing 101 may beprovided with lead terminals (not shown) for inputting power to thelight emitting diode chip 102. The housing 101 may include a mountingregion for mounting the light emitting diode chip 102, and the lightemitting diode chip 102 may be mounted on the mounting region through apaste or the like. The first and second phosphors 105, 106 may bedistributed within the wavelength converter 104, and the wavelengthconverter 104 may cover at least part of the light emitting diode chip102.

The housing 101 may be formed of general plastics including polymers andthe like, acrylonitrile butadiene styrene (ABS), liquid crystallinepolymers (LCPs), polyamide (PA), polyphenylene sulfide (IPS),thermoplastic elastomers (TPEs), metals, or ceramics. However, amaterial for the housing 101 is not limited thereto. In addition, thehousing 101 may have an inclined inner wall for reflection of lightbeams emitted from the light emitting diode chip 102 and the first andsecond phosphors 105, 106.

The wavelength converter 104 may be formed of a material including atleast one of silicone, epoxy, poly(methyl methacrylate) (PMMA),polyethylene (PE), and polystyrene (PS). The wavelength converter 104may be formed by injection molding using a mixture of the above materialand the first and second phosphors 105, 106. Alternatively, thewavelength converter 104 may be formed by fabricating a molded productusing a separate mold, followed by pressing or heat-treating the moldedproduct. The wavelength converter 104 may be formed in various shapessuch as a convex lens shape, a flat plate shape (not shown), and a shapehaving a surface embossed in a predetermined pattern. Although thewavelength converter 104 is shown as having a convex lens shape herein,it should be understood that the shape of the wavelength converter 104is not limited thereto.

In this exemplary embodiment, the light emitting diode chip 102 may emitlight having a peak wavelength of 415 nm to 430 nm. In addition, thelight emitting diode chip 102 may emit light having a full width at halfmaximum (FWHM) of 40 nm or less at the peak wavelength.

Although the light emitting device is shown as including one lightemitting diode chip 102 herein, it should be understood that otherimplementations are also possible. The light emitting device accordingto the exemplary embodiment may further include at least one lightemitting diode chip that emits light having the same peak wavelength asthe light emitting diode chip 102 or light having a different peakwavelength.

The first phosphor 105 and the second phosphor 106 may be excited by thelight emitted from the light emitting diode chip 102. The first phosphor105 may be excited to emit light having a peak wavelength in the cyanwavelength band, and the second phosphor 106 may be excited to emitlight having a peak wavelength in the red wavelength band.

The peak wavelength of the light emitted from the first phosphor 105 maybe in the range of 500 nm to 540 nm. The first phosphor 105 may includeat least one of LuAG, YAG, beta-SiAlON, nitride, and silicate phosphors,without being limited thereto. As the first phosphor 105, any phosphormay be used so long as the phosphor can be excited by light from thelight emitting diode chip 102 to emit light having a peak wavelength inthe cyan wavelength band within the range of 500 nm to 540 nm. When thefirst phosphor 105 includes an LuAG phosphor, the LuAG phosphor mayinclude a phosphor represented by Lu_(x)Al_(y)O_(z):Ce orLu_(x)(Al,Ga)_(y)O_(z):Ce.

The peak wavelength of the light emitted from the second phosphor 106may be in the range of 600 nm to 650 nm. The second phosphor 106 may bea nitride phosphor represented by CASN, CASON, and SCASN, without beinglimited thereto.

Electromagnetic radiation visible to the human eye has a wavelength of380 nm to 760 nm, and the human eye finds green light at 555 nm to bebrightest. Thus, the human eye perceives light having a wavelengthlonger than or shorter than 555 nm to as being less bright. This may beexpressed as a value obtained by dividing luminous flux Fλ (unit: lm) ofwavelength λ by radiant flux ρ (unit: W), that is, Fλ/ρ (lm/W), andluminous efficacy of green light having a wavelength of 555 nm isreferred to as maximum luminous efficacy. Thus, in order to increaseluminous intensity of white light from the light emitting deviceperceived by the human eye, that is, luminous efficacy, the lightemitting device is required to emit light having an optical spectrumconcentrated around 555 nm.

In this exemplary embodiment, the light emitting diode chip 102 may emitlight having a peak wavelength of 415 nm to 430 nm, the first phosphor105 is excited by light from the light emitting diode chip 102 to emitlight having a peak wavelength of 500 nm to 540 nm, and the secondphosphor 106 is excited by light from the light emitting diode chip 102to emit light having a peak wavelength of 600 nm to 650 nm. Accordingly,white light emitted from the light emitting device has an opticalspectrum concentrated around light having the maximum luminous efficacy,that is, green light having a wavelength of 555 nm. More specifically,40% or more of an optical spectrum of the white light emitted from thelight emitting diode according to this exemplary embodiment may bedistributed within the wavelength range of 500 nm to 600 nm around 555nm.

A typical light emitting device using a blue light-emitting diode chipuses phosphors that emit light having a relatively long peak wavelengthin the red wavelength band. Thus, it is difficult for such a typicallight emitting device to emit white light having an optical spectrumconcentrated around light having a wavelength of 555 nm. The lightemitting device according to this exemplary embodiment can emit whitelight having a high luminous efficacy and luminous intensity, ascompared with typical light emitting devices. Further, since the lightemitting device according to this exemplary embodiment does not includean ultraviolet light emitting diode chip, it is possible to preventpackage components from being damaged due to ultraviolet light emittedfrom the ultraviolet light emitting diode chip. Light emitted from thelight emitting device according to this exemplary embodiment may have acolor rendering index (CRI) of 85 or higher. Specifically, the lightemitted from the light emitting device according to this exemplaryembodiment may have a CRI of 90 or higher.

Experimental Example 1

In order to confirm that the light emitting device according to thisexemplary embodiment can provide enhanced luminous efficacy and luminousintensity, a test was conducted as follows: First, for comparison, twolight emitting device samples were prepared. Sample 1 is a typical lightemitting device and includes a light emitting diode chip emitting lighthaving a peak wavelength of 450 nm, a cyan phosphor represented byLu₃Al₅O₁₂:Ce, and a red phosphor represented by CaAlSiN₃:Eu. Sample 2 isa light emitting device according to the embodiment of the presentdisclosure and includes a light emitting diode chip emitting lighthaving a peak wavelength of 425 nm, a cyan phosphor (first phosphor)represented by Lu₃(Al,Ga)₅O₁₂:Ce, and a red phosphor (second phosphor)represented by (Sr,Ca)AlSiN₃:Eu. Current applied to the two lightemitting device samples was 100 mA and testing was carried out under thesame conditions.

As a result of analyzing white light emitted from Sample 1 and Sample 2,Sample 1 exhibited a luminous efficacy of 109.5 lm/W and Sample 2exhibited a luminous efficacy of 115.1 lm/W. In addition, with the samecolor coordinates, Sample 1 exhibited a luminous intensity (flux) of33.35 lm, and Sample 2 exhibited a luminous intensity (flux) of 36.08lm. Further, Sample 1 exhibited a CRI of 90, and Sample 2 exhibited aCRI of 92.5. In other words, it could be seen that the light emittingdevice according to the exemplary embodiments of the present disclosurewas improved in luminous efficacy, luminous intensity, and CRI, ascompared with the typical light emitting device. Particularly, theluminous efficacy and the luminous intensity (flux) of the lightemitting device according to the exemplary embodiment of the presentdisclosure was improved by 5.1% and 8.2%, respectively, as compared withthose of the typical light emitting device.

FIG. 2 is a schematic sectional view of a light emitting deviceaccording to another exemplary embodiment of the present disclosure.

Referring to FIG. 2, the light emitting device according to thisexemplary embodiment includes a housing 101, a light emitting diode chip102, a wavelength converter 104, a first phosphor 105, a second phosphor106, and a third phosphor 107. The light emitting device according tothis exemplary embodiment is substantially the same as the lightemitting device according to the above exemplary embodiment except forthe third phosphor 107. Thus, repeated descriptions of the samecomponents will be omitted.

Referring to FIG. 2, the light emitting device according to thisexemplary embodiment includes the third phosphor. The third phosphor 107may emit light having a peak wavelength in the blue wavelength band.Specifically, the third phosphor 107 may be excited by light emittedfrom the light emitting diode chip 102 to emit light having a peakwavelength of 450 nm to 480 nm. The third phosphor 107 may include atleast one of SBCA, BAM (Ba—Al—Mg), silicate, and nitride phosphors,without being limited thereto. Any phosphor may be used as the thirdphosphor 107 so long as the phosphor can be excited by light having apeak wavelength of 415 nm to 430 nm from the light emitting diode chip102 to emit light having a peak wavelength of 450 nm to 480 nm.

Experimental Example 2

In order to confirm that the light emitting device according to thisexemplary embodiment, which further includes the third phosphor 107, canprovide enhanced luminous efficacy and luminous intensity, a test wasconducted as follows: Sample 1 of Experimental example 1 was used as atypical light emitting device sample. Sample 3 was prepared as a sampleof the light emitting device according to this exemplary embodiment.Here, Sample 3 was a light emitting device including a light emittingdiode chip having a peak wavelength of 425 nm, a cyan phosphor (firstphosphor) represented by Lu₃(Al,Ga)₅O₁₂:Ce, a red phosphor (secondphosphor) represented by (Sr,Ca)AlSiN₃:Eu, and a blue phosphor (thirdphosphor) represented by (Sr,Ba)₁₀(PO₄)₆Cl₂:Eu. The current applied tothe two light emitting device samples was 100 mA, and the test wascarried out under the same conditions.

As a result of analyzing white light emitted from Sample 1 and Sample 3,Sample 1 exhibited a luminous efficacy of 109.5 lm/W, and Sample 2exhibited a luminous efficacy of 116.5 lm/W. In addition, with the samecolor coordinates, Sample 1 exhibited a luminous intensity (flux) of33.35 lm and Sample 2 exhibited a luminous intensity (flux) of 36.57 lm.Further, Sample 1 exhibited a CRI of 90 and Sample 2 exhibited a CRI of92. Thus, it could be seen that the light emitting device according tothis exemplary embodiment was improved in terms of luminous efficacy,luminous intensity, and CRI, as compared with the typical light emittingdevice. Specifically, the luminous efficacy and luminous intensity(flux) of the light emitting device according to this exemplaryembodiment was improved by 6.4% and 9.7%, respectively, as compared withthose of the typical light emitting device. FIG. 7 is a graph comparingoptical spectra of the light emitting device according to this exemplaryembodiment and the typical light emitting device. Referring to FIG. 7,Line a represents the optical spectrum of Sample 1, which is the typicallight emitting device sample, and Line b represents the optical spectrumof Sample 3, which is the light emitting device according to thisexemplary embodiment. As shown in the graph, it can be seen that theoptical spectrum of Sample 3 is more concentrated around 555 nm, whichis a wavelength exhibiting the maximum luminous efficacy, than that ofthe typical light emitting device.

FIG. 3 is a schematic sectional view of a light emitting deviceaccording to a further exemplary embodiment of the present disclosure.

Referring to FIG. 3, the light emitting device according to thisexemplary embodiment includes a housing 101, a light emitting diode chip102, a wavelength converter 104, a first phosphor 105, a secondphosphor, and a buffer portion 109. The light emitting device accordingto this exemplary embodiment is substantially similar to the lightemitting device according to the above embodiment except for the bufferportion 109. Thus, repeated descriptions of the same components will beomitted.

The buffer portion 109 may be disposed between the light emitting diodechip 102 and the wavelength converter 104. The buffer portion may beformed of a material including at least one of silicone, epoxy,poly(methyl methacrylate) (PMMA), polyethylene (PE), and polystyrene(PS). The buffer portion 109 may have lower hardness than the wavelengthconverter 104. The buffer portion 109 serves to prevent thermal stressof the wavelength converter 104 due to heat generated in the lightemitting diode chip 102. Although the buffer portion 109 is shown asdisposed around the light emitting diode chip 102, it should beunderstood that the buffer portion may be disposed over a wide area toadjoin right and left walls of the housing 101.

FIG. 4 is a schematic sectional view of a light emitting deviceaccording to yet another exemplary embodiment of the present disclosure.

Referring to FIG. 4, the light emitting device according to thisexemplary embodiment may include a housing 101, a light emitting diodechip 102, a wavelength converter 104, a first phosphor 105, a secondphosphor 106, a reflector 111, and a barrier reflector 112. The lightemitting device according to this exemplary embodiment is substantiallysimilar to the light emitting device according to the above embodimentexcept for the reflector 111 and the barrier reflector 112. Thus,repeated descriptions of the same components will be omitted.

The reflector 111 may be disposed on a side surface of the housing awayfrom the light emitting diode chip 102. The reflector 111 serves tomaximize reflection of light emitted from the light emitting diode chip102 and the first and second phosphors 105, 106, thereby increasingluminous efficiency. The reflector 111 may be any one of a reflectivecoating film and a reflective coating material layer. The reflector 111may be formed of at least one of inorganic materials, organic materials,metals, and metal oxides having excellent heat resistance and lightresistance. For example, the reflector 111 may include a metal or metaloxide having high reflectance, such as aluminum (Al), silver (Ag), gold(Au), and titanium dioxide (TiO₂). The reflector 111 may be formed bydepositing or coating the metal or the metal oxide on the housing 101 orby printing a metal ink on the housing. Alternatively, the reflector 111may be formed by attaching a reflective film or a reflective sheet tothe housing 101.

The barrier reflector 112 may cover the reflector 111. The barrierreflector 112 serves to prevent degradation of the reflector 111 due toheat emitted from the light emitting diode chip 102. The barrierreflector 112 may be formed of an inorganic material or a metal havinghigh light resistance and reflectivity.

FIG. 5 is a schematic sectional view of a light emitting deviceaccording to yet another exemplary embodiment of the present disclosure.

Referring to FIG. 5, the light emitting device according to thisexemplary embodiment includes a housing 101, a light emitting diode chip102, a wavelength converter 104, a first phosphor 105, and a secondphosphor 106, wherein the wavelength converter 104 may include a firstwavelength converter 104 b and a second wavelength converter 104 a. Thelight emitting device according to this exemplary embodiment issubstantially similar to the light emitting device according to theabove embodiment except for the first wavelength converter 104 b and thesecond wavelength converter 104 a. Thus, repeated descriptions of thesame components will be omitted.

The first wavelength converter 104 b may cover the first and secondlight emitting diode chips 102, 103. The second wavelength converter 104a may cover the first wavelength converter 104 b. The first wavelengthconverter 104 b may be formed of a material having the same hardness asthe second wavelength converter 104 a, or may be formed of a materialhaving a different hardness. In this exemplary embodiment, the firstwavelength converter 104 b may have lower hardness than the secondwavelength converter 104 a. In this case, like the buffer portion 109 inthe aforementioned embodiment, the first wavelength converter canprevent thermal stress of the second wavelength converter due to heatgenerated in the light emitting diode chips 102, 103.

The first wavelength converter 104 b may contain the second phosphor 106that emits light having a peak wavelength in the red wavelength band.The second wavelength converter 104 a may contain the first phosphor 105that emits light having a peak wavelength in the cyan wavelength band.In this exemplary embodiment, phosphors emitting light at longerwavelengths are disposed on the lower side and phosphors emitting lightat shorter wavelengths are disposed on the upper side, whereby the lightemitting device can prevent cyan light emitted from the first phosphor105 from being reabsorbed to cause light loss by the second phosphor106.

FIG. 6 is a schematic sectional view of a light emitting deviceaccording to yet another exemplary embodiment of the present disclosure.

Referring to FIG. 6, the light emitting device according to thisexemplary embodiment includes a housing 101, a light emitting diode chip102, a wavelength converter 104, a first phosphor 105, a second phosphor106, and a phosphor plate 118. The light emitting device according tothis exemplary embodiment is substantially similar to the light emittingdevice according to the above embodiment except for the phosphor plate118. Thus, repeated descriptions of the same components will be omitted.

The phosphor plate 118 is disposed on the wavelength converter 104 to bespaced apart from the light emitting diode chip 102 and may contain thefirst and second phosphors 105, 106. The phosphor plate 118 may beformed of the same material as the wavelength converter 104 according tothe above exemplary embodiment or a material having high hardness.

Since the first and second phosphors 105, 106 are spaced apart from thelight emitting diode chip 102, damage to the first and second phosphors105, 106 and the phosphor plate 118 due to heat or light can be reduced.As a result, it is possible to improve reliability of the first andsecond phosphors 105, 106. Alternatively, an empty space may be formedbetween the phosphor plate 118 and the light emitting diode chip 102,instead of the wavelength converter 104.

FIG. 8 is a sectional view of a light emitting device according to yetanother exemplary embodiment of the present disclosure.

Referring to FIG. 8, the light emitting device according to thisexemplary embodiment includes a light emitting diode 102, a wavelengthconverter 130, and a housing 101.

In this exemplary embodiment, the light emitting diode 102 may bedisposed on the housing 101. Here, the housing may be, for example, abase, as shown in the drawing.

The housing may include a cavity open upward, and the light emittingdiode 102 may be mounted in the cavity. The cavity may have an inclinedinner side surface such that light emitted from the light emitting diode102 can be reflected from the side surface, thereby improving luminousefficiency of the light emitting device according to this exemplaryembodiment. In addition, a reflective material may be further disposedon the inner side surface of the cavity.

When the base is formed as a housing, the housing may be formed ofgeneral plastics including polymers and the like, acrylonitrilebutadiene styrene (ABS), liquid crystalline polymers (LCPs), polyamide(PA), polyphenylene sulfide (IPS), thermoplastic elastomers (TPEs),metals, or ceramics. However, it should be understood that otherimplementations are also possible.

In addition, the housing 101 may include at least two lead terminals andthe light emitting diode 102 may be electrically connected to the leadterminals. Through the lead terminals, the light emitting device can beconnected to an external power source. Alternatively, the light emittingdiode 102 may be located on the lead terminals.

Further, the housing 101 may further include any known componentscapable of supporting the light emitting diode 102. For example, thehousing 101 may include a PCB or a conductive or insulating substrate onwhich the light emitting diode 102 is mounted, such as a lead frame, andmay include a heat sink or the like for dissipating heat generated fromthe light emitting diode 102.

The light emitting diode 102 may include an n-type semiconductor layerand a p-type semiconductor layer to emit light through recombination ofholes and electrons. The light emitting diode 102 may be a horizontal,vertical, or flip chip-type light emitting diode, and the configurationand shape of the light emitting diode 102 are not particularly limited.

The light emitting diode 102 can emit light having a peak wavelength inthe visible range, particularly, light having a peak wavelength of 415nm to 435 nm. With the light emitting diode 102 that emits light havinga peak wavelength in the above range, the light emitting device canprevent reduction in reliability and luminous efficiency due to use ofan ultraviolet light emitting diode and can minimize light emission atabout 450 nm, thereby minimizing harmfulness to the human body.

The wavelength converter 130 may be disposed on the light emitting diode102 to cover at least part of the light emitting diode 102 or toencapsulate the light emitting diode 102. That is, the wavelengthconverter 130 may be positioned on a light emission path of the lightemitting diode 102.

The wavelength converter 130 may include a support 131; and a redphosphor 135, green phosphor 137, and cyan phosphor 139 irregularlydispersed in the support 131.

The support 131 may be formed of any material capable of supporting thephosphors 135, 137, 139, and may be transparent or translucent. Thesupport 131 may be formed of, for example, a polymer including at leastone of silicone, epoxy, poly(methyl methacrylate) (PMMA), andpolyethylene (PE), or an inorganic material such as glass.

When the support 131 is formed of a polymer, the wavelength converter130 may function as an encapsulant encapsulating the light emittingdiode 102 while functioning to convert the wavelength of light emittedfrom the light emitting diode 102. In addition, the wavelength converter130 may be disposed on the housing 101. When the housing 101 includes acavity, as in this exemplary embodiment, the wavelength converter 130may be placed in the cavity. Further, an upper surface of the wavelengthconverter 130 may be formed in various shapes such as a convex lensshape, a flat plate shape (not shown), and a shape embossed in apredetermined pattern. Although the wavelength converter 130 is shown ashaving a convex lens shape herein, it should be understood that theshape of the wavelength converter is not limited thereto.

The red phosphor 135, the green phosphor 137, and the cyan phosphor 139may be irregularly distributed in the support 131.

Specifically, the red phosphor 135 may be excited by incident light toemit red light, the green phosphor 137 may be excited by incident lightto emit green light, and the cyan phosphor 139 may be excited byincident light to emit cyan light. Accordingly, the light emittingdevice according to this exemplary embodiment can emit white lightthrough combination of violet light emitted from the light emittingdiode 102 with the red light emitted from the red phosphor 135, thegreen light emitted from the green phosphor 137, and the cyan lightemitted from the cyan phosphor 139.

In addition, the white light from the light emitting device according tothis exemplary embodiment may have a CRI of 90 or higher.

The peak wavelength of the red light emitted from the red phosphor 135may be in the range of 600 nm to 660 nm. The red phosphor 135 includes afirst red phosphor 133 and a second red phosphor 134.

The first red phosphor 133 includes a phosphor represented by A₂MF₆:Mn,wherein A is any one selected from the group consisting of Li, Na, K,Rb, Ce, and NH₄, and M is any one selected from the group consisting ofSi, Ti, Nb, and Ta. The first red phosphor 133 may emit light having apeak wavelength of 625 nm to 660 nm. The second red phosphor 134 mayinclude a CASN phosphor. The CASN phosphor may emit light having a peakwavelength of 600 nm to 650 nm. The CASN phosphor may include a phosphorrepresented by (Sr,Ca)AlSiN₃:EU or CaAlSiN₃:EU.

The green phosphor 137 may include a silicate phosphor. The silicatephosphor may emit light having a peak wavelength of 520 nm to 550 nm.The silicate phosphor may include a phosphor represented by(Ba,Sr,Ca)₂SiO₄:EU.

The cyan phosphor 139 may include an LuAG phosphor. The LuAG phosphormay emit light having a peak wavelength of 490 nm to 550 nm. The LuAGphosphor may include a phosphor represented by Lu₃Al₅O₁₂:Ce orLu₃(Al,X)₅O₁₂:Ce (where X is a group III element other than Al, and Alis partially substituted with an element of the same group, such as Gaor In). Specifically, the LuAG phosphor may include a phosphorrepresented by Lu₃(Al,Ga)₅O₁₂:Ce (where Al is partially substituted withGa). Particularly, the phosphor represented by Lu₃(Al,Ga)₅O₁₂:Ce mayemit light having a peak wavelength of 490 nm to 520 nm, specificallyabout 505 nm.

In the wavelength converter, a weight ratio of the second red phosphor134 to the first red phosphor 133 may be 2.5 to 5:7.5 to 5.Specifically, in the wavelength converter, a weight ratio of thephosphor represented by (Sr,Ca)AlSiN₃:EU or CaAlSiN₃:EU to the phosphorrepresented by A₂MF₆:Mn may be 2.5 to 5:7.5 to 5, wherein A is any oneselected from the group consisting of Li, Na, K, Rb, Ce, and NH₄, and Mis any one selected from the group consisting of Si, Ti, Nb, and Ta.

In the wavelength converter, a weight ratio of the LuAG phosphor to thesilicate phosphor may be 8 to 9.9:0.1 to 2. Specifically, in thewavelength converter, a weight ratio of the phosphor represent byLu₃Al₅O₁₂:Ce or Lu₃(Al,X)₅O₁₂:Ce (where X is a group III element otherthan Al) to the phosphor represented by (Ba,Sr,Ca)₂SiO₄:EU may be 8 to9.9:0.1 to 2.

According to this exemplary embodiment, it is possible to provide alight emitting device which can provide a CRI of 90 or higher andexcellent luminous intensity.

Specifically, the white light emitting device according to thisexemplary embodiment may have a luminous intensity variation rate ofhigher than 100%, as calculated according to Equation 1.

Luminous intensity variation rate (%)=(F1/F0)×1/F  [Equation 1]

F₁: Luminous intensity (unit: lm) of light emitted from the lightemitting device

F₀: Luminous intensity (unit: lm) of light emitted from a light emittingdevice including a wavelength converter only including a LuAG phosphorrepresented by Lu₃(Al,Ga)₅O₁₂:Ce and a CASN phosphor represented by(Sr,Ca)AlSiN₃:EU as phosphors

Example and Comparative Example Example 1: Fabrication of Light EmittingDevice

Referring to FIG. 8, as a light emitting diode emitting a peakwavelength of about 425 nm, a rectangular light emitting chip having asize of 860 μm×μmghμm was mounted on a lead frame (not shown).

A housing having a cavity was formed at the upper end of the lead frameusing an epoxy molding compound (EMC) by transfer molding.

The phosphors according to the exemplary embodiments were mixed with 90%by weight of a silicone resin based on the total weight of thewavelength converter, thereby preparing a slurry, which was in turnpoured into the cavity of the housing. Then, the silicone resin wascured through heat treatment at 150° C., thereby fabricating a lightemitting device including a wavelength converter. Here, a predeterminednumber of phosphors were used such that an LED lamp had chromaticity(CIE) coordinates, x=0.458 to 0.462, y=0.412 to 0.417. In addition, inthe wavelength converter, a weight ratio of the second red phosphorrepresented by (Sr,Ca)AlSiN₃:EU to the first red phosphor represented byK₂SiF₆:Mn was 4:6, and a weight ratio of the LuAG phosphor representedby Lu₃(Al,Ga)₅O₁₂:Ce to the silicate phosphor represented by(Ba,Sr,Ca)₂SiO₄:EU was 9:1.

Comparative Example 1: Fabrication of Light Emitting Device

A light emitting device was fabricated in the same manner as in Example1 except that a weight ratio of the second red phosphor represented by(Sr,Ca)AlSiN₃:EU to the first red phosphor represented by K₂SiF₆:Mn was7:3.

Comparative Example 2: Fabrication of Light Emitting Device

A light emitting device was fabricated in the same manner as in Example1 except that a weight ratio of the second red phosphor represented by(Sr,Ca)AlSiN₃:EU to the first red phosphor represented by K₂SiF₆:Mn was2:8.

Comparative Example 3: Fabrication of Light Emitting Device

A light emitting device was fabricated in the same manner as in Example1 except that the first red phosphor represented by K₂SiF₆:Mn and thesilicate phosphor represented by (Ba,Sr,Ca)₂SiO₄:EU were not used.

Experimental Example

CRI and R9 values of each of the light emitting devices fabricated inExample 1 and Comparative Examples 1 to 3 were measured by supplyingpower (rated current: 100 mA, voltage: 6.1 V) to the light emittingdevices. In addition, after the flux (unit: lm) of each of the lightemitting devices fabricated in Example 1 and Comparative Examples 1 to 3was measured, the luminous intensity variation rate (A) of each of thelight emitting devices of Example and Comparative Examples was expressedin % relative to the measured flux of the light emitting device ofComparative Example 3. Results are shown in Table 1.

TABLE 1 L/ @equal CIE x, y Flux Flux Δ CIE x CIE y (lm) (lm) (%) CRI R9Example 1 0.460 0.413 71.0 71.7 104.4 91.1 40.0 Comparative 0.460 0.41672.3 72.3 105.4 89.1 33.5 Example 1 Comparative 0.460 0.416 67.9 67.999.0 94.5 60.2 Example 2 Comparative 0.460 0.416 68.0 68.6 100 92.4 43.6Example 3

Referring to Table 1, it can be seen that the light emitting deviceaccording to the exemplary embodiment had a CRI of 90 or higher and aluminous intensity variation rate of 104.4% and was thus increased influx, as compared with the light emitting device of Comparative Example3 not including the first red phosphor. Conversely, the light emittingdevice of Comparative Example 2 had a luminous intensity variation rateof 99.0% despite having a CRI of 90 or higher and was thus reduced inluminous intensity. In addition, it can be seen that the light emittingdevice of Comparative Example 1 exhibited a luminous intensity variationrate of 105.4% and was thus increased in luminous intensity, but had aCRI of 89.1 and thus exhibited poor color rendition. Since the numericalvalues of Comparative Example 3 are reference values, evaluation ofComparative Example 3 is meaningless.

FIG. 9 is a sectional view of a light emitting device according to yetanother exemplary embodiment of the present disclosure.

Referring to FIG. 9, the light emitting device according to thisexemplary embodiment includes a light emitting diode 102, a wavelengthconverter 130, and a housing 101.

In this exemplary embodiment, the light emitting diode 102 may bedisposed on the housing 101. Here, the housing may be, for example, abase as shown in the drawing.

The housing may include a cavity open upward, and the light emittingdiode 102 may be mounted in the cavity. The cavity may have an inclinedinner side surface, such that light emitted from the light emittingdiode 102 can be reflected from the side surface, thereby improvingluminous efficiency of the light emitting device according to thisexemplary embodiment. In addition, a reflective material may be furtherdisposed on the inner side surface of the cavity.

When the base is formed as a housing, the housing may be formed ofgeneral plastics including polymers and the like, acrylonitrilebutadiene styrene (ABS), liquid crystalline polymers (LCPs), polyamide(PA), polyphenylene sulfide (IPS), thermoplastic elastomers (TPEs),metals, or ceramics. However, it should be understood that otherimplementations are also possible.

In addition, the housing 101 may include at least two lead terminals,and the light emitting diode 102 may be electrically connected to thelead terminals. Through the lead terminals, the light emitting devicecan be connected to an external power source. Alternatively, the lightemitting diode 102 may be disposed on the lead terminals.

Further, the housing 101 may further include any known componentscapable of supporting the light emitting diode 102. For example, thehousing 101 may include a PCB or a conductive or insulating substrate onwhich the light emitting diode 102 is mounted, such as a lead frame, andmay include a heat sink or the like for dissipating heat generated fromthe light emitting diode 102.

The light emitting diode 102 may include an n-type semiconductor layerand a p-type semiconductor layer to emit light through recombination ofholes and electrons. The light emitting diode 102 may be a horizontal,vertical, or flip chip-type light emitting diode, and the configurationand shape of the light emitting diode 102 are not particularly limited.

The light emitting diode 102 can emit light having a peak wavelength inthe visible range, particularly, light having a peak wavelength of 415nm to 435 nm. Using the light emitting diode 102 that emits light havinga peak wavelength in the above range, it is possible to preventreduction in reliability and luminous efficiency of the light emittingdevice due to use of an ultraviolet light emitting diode and to minimizelight emission at about 450 nm, thereby minimizing harmfulness to thehuman body.

The wavelength converter 130 may be placed on the light emitting diode102 to cover at least part of the light emitting diode 102 or toencapsulate the light emitting diode 102. That is, the wavelengthconverter 130 may be positioned on a light emission path of the lightemitting diode 102.

The wavelength converter 130 may include: a support 131; and a redphosphor 134 and a cyan phosphor 139 irregularly dispersed in thesupport 131.

The support 131 may be formed of any material capable of supportingfirst and second red phosphors 133, 135, and may be transparent ortranslucent. The support 131 may be formed of, for example, a polymerincluding at least one of silicone, epoxy, poly(methyl methacrylate)(PMMA), and polyethylene (PE), or an inorganic material such as glass.

When the support 131 is formed of a polymer, the wavelength converter130 may function as an encapsulant encapsulating the light emittingdiode 102 while functioning to convert the wavelength of light emittedfrom the light emitting diode 102. In addition, the wavelength converter130 may be disposed on the housing 101. When the housing 101 includes acavity, as in this exemplary embodiment, the wavelength converter 130may be placed in the cavity. Further, an upper surface of the wavelengthconverter 130 may be formed in various shapes such as a convex lensshape, a flat plate shape (not shown), and a shape embossed in apredetermined pattern. Although the wavelength converter 130 is shown ashaving a convex lens shape herein, it should be understood that theshape of the wavelength converter is not limited thereto.

The red phosphor 134 and the cyan phosphor 139 may be irregularlydistributed in the support 131.

Specifically, the red phosphor 134 may be excited by incident light toemit red light, and the cyan phosphor 139 may be excited by incidentlight to emit cyan light. Accordingly, the light emitting deviceaccording to this exemplary embodiment can emit white light throughcombination of violet light emitted from the light emitting diode 102with the red light emitted from the red phosphor 134 and the cyan lightemitted from the cyan phosphor 139.

In addition, the white light from the light emitting device according tothis exemplary embodiment may have a CRI of 90 or higher. Further, thewhite light from the light emitting device according to this exemplaryembodiment may have an R9 of 50 or higher.

The peak wavelength of the red light emitted from the red phosphor 134may be in the range of 600 nm to 660 nm. The red phosphor 134 includes afirst red phosphor 133 and a second red phosphor 134.

The first red phosphor 133 includes a phosphor represented by A₂MF₆:Mn,wherein A is any one selected from the group consisting of Li, Na, K,Rb, Ce, and NH₄, and M is any one selected from the group consisting ofSi, Ti, Nb, and Ta. The first red phosphor 133 may emit light having apeak wavelength of 625 nm to 660 nm.

The second red phosphor 134 may include a CASN phosphor. The CASNphosphor may emit light having a peak wavelength of 600 nm to 650 nm.The CASN phosphor may include a phosphor represented by (Sr,Ca)AlSiN₃:EUor CaAlSiN₃:EU.

The cyan phosphor 139 may include an LuAG phosphor. The LuAG phosphormay emit light having a peak wavelength of 490 nm to 550 nm. The LuAGphosphor may include a phosphor represented by Lu₃Al₅O₁₂:Ce orLu₃(Al,X)₅O₁₂:Ce (where X is a group III element other than Al, and Alis partially substituted with an element of the same group, such as Gaor In). Specifically, the LuAG phosphor may include a phosphorrepresented by Lu₃(Al,Ga)₅O₁₂:Ce (where Al is partially substituted withGa). Particularly, the phosphor represented by Lu₃(Al,Ga)₅O₁₂:Ce mayemit light having a peak wavelength of 490 nm to 520 nm, specificallyabout 505 nm.

In the wavelength converter, a weight ratio of the second red phosphor134 to the first red phosphor 133 may be 0.5 to 4:6.5 to 9.5.Specifically, in the wavelength converter, a weight ratio of thephosphor represented by (Sr,Ca)AlSiN₃:EU or CaAlSiN₃:EU to the phosphorrepresented by A₂MF₆:Mn may be 0.5 to 4:6.5 to 9.5, wherein A is any oneselected from the group consisting of Li, Na, K, Rb, Ce, and NH₄, and Mis any one selected from the group consisting of Si, Ti, Nb, and Ta.

According to the exemplary embodiment, the light emitting device canprovide a CRI of 90 or higher and an R9 of 50 or higher and exhibitexcellent luminous intensity. Specifically, the light emitting devicehas a CRI of 90 or higher and an R9 of 50 and is reduced in luminousintensity by only 1% as compared with a typical light emitting deviceusing only a CASN-based short wavelength red phosphor in combinationwith a violet light emitting diode and thus exhibits good luminousintensity.

Specifically, the white light emitting device according to thisexemplary embodiment may have a luminous intensity variation rate of98.8% or higher, as calculated according to Equation 1.

Luminous intensity variation rate (%)=(F1/F0)×100.  [Equation 1]

F₁: Luminous intensity (unit: lm) of light emitted from the lightemitting device

F₀: Luminous intensity (unit: lm) of light emitted from a light emittingdevice including a wavelength converter only including a CASN phosphorrepresented by (Sr,Ca)AlSiN₃:EU and an LuAG phosphor represented byLu₃Al₅O₁₂:Ce or Lu₃(Al,X)₅O₁₂:Ce (where X is a group III element otherthan Al) as phosphors

Example and Comparative Example Example 2: Fabrication of Light EmittingDevice

Referring to FIG. 9, as a light emitting diode emitting a peakwavelength of about 425 nm, a rectangular light emitting chip having asize of 860 μm×540 μm was mounted on a lead frame (not shown).

A housing having a cavity was formed at the upper end of the lead frameusing an epoxy molding compound (EMC) by transfer molding.

The phosphors according to the exemplary embodiments were mixed with 90%by weight of a silicone resin based on the total weight of thewavelength converter, thereby preparing a slurry, which was in turnpoured into the cavity of the housing. Then, the silicone resin wascured through heat treatment at 150° C., thereby fabricating a lightemitting device including a wavelength converter. Here, a predeterminednumber of phosphors were used such that an LED lamp had chromaticity(CIE) coordinates, x=0.458 to 0.462, y=0.409 to 0.417.

In addition, the wavelength converter included the second red phosphorrepresented by (Sr,Ca)AlSiN₃:EU and the first red phosphor representedby K₂SiF₆:Mn in a weight ratio of 3:7 and also included an LuAG phosphorrepresented by Lu₃(Al,Ga)₅O₁₂:Ce.

Example 3: Fabrication of Light Emitting Device

A light emitting device was fabricated in the same manner as in Example2 except that a weight ratio of the second red phosphor represented by(Sr,Ca)AlSiN₃:EU to the first red phosphor represented by K₂SiF₆:Mn was2:8.

Comparative Example 4: Fabrication of Light Emitting Device

A light emitting device was fabricated in the same manner as in Example2 except that the first red phosphor represented by K₂SiF₆:Mn was notused.

Comparative Example 5: Fabrication of Light Emitting Device

A light emitting device was fabricated in the same manner as in Example2 except that a CASN phosphor represented by CaAlSiN₃: EU was usedinstead of the first red phosphor represented by K₂SiF₆:Mn, and a weightratio of the second red phosphor represented by (Sr,Ca)AlSiN₃:EU to theCASN phosphor represented by CaAlSiN₃ was 7:3.

Comparative Example 6: Fabrication of Light Emitting Device

A light emitting device was fabricated in the same manner as in Example2 except that a weight ratio of the second red phosphor represented by(Sr,Ca)AlSiN₃:EU to the first red phosphor represented by K₂SiF₆:Mn was4:6.

Comparative Example 7: Fabrication of Light Emitting Device

A light emitting device was fabricated in the same manner as in Example2 except that a weight ratio of the second red phosphor represented by(Sr,Ca)AlSiN₃:EU to the first red phosphor represented by K₂SiF₆:Mn was7:3.

Experimental Example

CRI and R9 values of each of the light emitting devices fabricated inExample 2 and Comparative Examples 4 to 4 were measured by supplyingpower (rated current: 100 mA, voltage: 6.1 V) to the light emittingdevices. In addition, after the flux (unit: lm) of each of the lightemitting devices fabricated in Example 2 and Comparative Examples 4 to 4was measured, the luminous intensity variation rate (A) of each of thelight emitting devices of Examples and Comparative Examples wasexpressed in % relative to the measured flux of the light emittingdevice of Comparative Example 4. Results are shown in Table 2.

TABLE 2 L/ @equal CIE x, y Flux Flux Δ CIE x CIE y (lm) (lm) (%) CRI R9Example 2 0.460 0.416 68.4 68.4 99.7 93.0 53.4 Example 3 0.460 0.41667.9 67.9 99.0 93.7 61.2 Comparative 0.460 0.416 68.0 68.6 100.0 92.443.6 Example 4 Comparative 0.460 0.416 65.5 65.5 95.5 93.6 53.1 Example5 Comparative 0.460 0.410 67.9 69.2 100.9 92.5 48.2 Example 6Comparative 0.460 0.413 68.6 69.3 101.0 92.9 45.5 Example 7

As shown in Table 2, the light emitting devices of Examples 2 and 3 hada CRI of 90 or higher, an R9 of 50 or higher, and a luminous intensityvariation rate of 99.0% or 99.7%. Thus, it can be seen that the lightemitting devices according to the exemplary embodiments of the presentdisclosure were reduced in luminous intensity by only 1% or less, ascompared with the light emitting device of Comparative Example 4 notusing the first red phosphor and thus exhibited good luminous intensity.Conversely, the light emitting devices of Comparative Examples 4, 3, and4 had a CRI of 90 or higher and an R9 of 50 or less, and the lightemitting device of Comparative Example 5 had a CRI of 90 or higher andan R9 of 50 or higher, but had a luminous intensity variation rate of95.5% and thus was reduced in luminous intensity by 4% or more, ascompared with the light emitting device of Comparative Example 4 notusing the first red phosphor. Therefore, it can be seen that phosphorsare required to be used in a specific weight ratio so as to provide alight emitting device having a CRI of 90 or higher, an R9 of 50 orhigher, and excellent luminous intensity.

Although some exemplary embodiments have been described herein, itshould be understood that these embodiments are provided forillustration only and are not to be construed in any way as limiting thepresent disclosure, and that various modifications, changes,alterations, and equivalent embodiments can be made by those skilled inthe art without departing from the spirit and scope of the presentdisclosure. The scope of the present disclosure should be defined by theappended claims and equivalents thereof.

What is claimed is:
 1. A white light emitting device, comprising: ahousing including a mounting region; a light emitting diode chip mountedon the mounting region and configured to emit light having a peakwavelength in a blue wavelength band and a Full Width at Half Maximum(FWHM) of 40 nm or less at the peak wavelength; a wavelength converterdisposed on the light emitting diode chip; a first phosphor distributedin the wavelength converter and configured to emit light having a peakwavelength in a green wavelength band; a second phosphor distributed inthe wavelength converter and configured to emit light having a peakwavelength in a red wavelength band; and a third phosphor distributed inthe wavelength converter and configured to emit light having a peakwavelength in a blue wavelength band, wherein: the first phosphorincludes a first green phosphor and a second green phosphor and thefirst green phosphor and the second green phosphor are formed ofdifferent materials; the second phosphor includes a first red phosphorand a second red phosphor and the first red phosphor and the second redphosphor are formed of different materials; the third phosphor isexcited by the light emitted from the light emitting diode chip to emitlight having a peak wavelength of 450 nm to 480 nm, and a white light isconfigured to be formed by a synthesis of light emitted from the lightemitting diode chip, the first phosphor, the first red phosphor, and thesecond red phosphor.
 2. The white light emitting device of claim 1,wherein the first phosphor includes at least one of LuAG, YAG, nitride,and silicate phosphors.
 3. The white light emitting device of claim 1,wherein the second phosphor includes at least one of CASN, CASON, andSCASN phosphors.
 4. The white light emitting device of claim 1, whereinthe third phosphor includes at least one of SBCA, BAM, silicate, andnitride phosphors.
 5. The white light emitting device of claim 1,wherein the wave length converter includes at least one of silicone,epoxy, PMMA, PE, and PS.
 6. The white light emitting device of claim 1,wherein the peak wavelength of the light emitting diode chip is shorterthan the third phosphor thereof.
 7. The white light emitting device ofclaim 6, wherein the light emitting diode chip emits light having a peakwavelength of 415 nm to 435 nm.
 8. The white light emitting device ofclaim 1, further comprises a reflector configured to serve to maximizereflection of light emitted from the light emitting diode chip and thefirst, second and third phosphors.
 9. The white light emitting device ofclaim 8, wherein the reflector includes a metal or metal oxide havinghigh reflectance, such as aluminum (Al), silver (Ag), gold (Au), andtitanium dioxide (TiO₂).
 10. The white light emitting device of claim 1,wherein the light emitting device is configured to emit white lightgenerated by combination of light from the light emitting diode chipwith light from the first phosphor and light from the second phosphor,the white light having a color rendering index (CRI) of 85 or higher.11. A white light emitting device, comprising: a housing including amounting region; a light emitting diode chip mounted on the mountingregion and configured to emit light having a peak wavelength in a bluewavelength band and a Full Width at Half Maximum (FWHM) of 40 nm or lessat the peak wavelength; a wavelength converter disposed on the lightemitting diode chip; a first phosphor distributed in the wavelengthconverter and configured to emit light having a peak wavelength in agreen wavelength band; a second phosphor distributed in the wavelengthconverter and configured to emit light having a peak wavelength in a redwavelength band; and wherein: the first phosphor includes a first greenphosphor and a second green phosphor and the first green phosphor andthe second green phosphor are formed of different materials; the secondphosphor includes a first red phosphor and a second red phosphor and thefirst red phosphor and the second red phosphor are formed of differentmaterials; the first green phosphor comprises a phosphor represented byLu₃Al₅O₁₂:Ce or Lu₃(Al, X)₅O₁₂:Ce wherein X is a group III element otherthan Al, and Al is partially substituted with a group III element otherthan Al, the first red phosphor comprises at least one of CASN, CASON,and SCASN phosphors, and a white light is configured to be formed by asynthesis of light emitted from the light emitting diode chip, the firstphosphor, the first red phosphor, and the second red phosphor.
 12. Thewhite light emitting device of claim 11, wherein the wave lengthconverter includes at least one of silicone, epoxy, PMMA, PE, and PS.13. The white light emitting device of claim 11, further comprises areflector configured to serve to maximize reflection of light emittedfrom the light emitting diode chip and the first, second and thirdphosphors.
 14. The white light emitting device of claim 13, wherein thereflector includes a metal or metal oxide having high reflectance, suchas aluminum (Al), silver (Ag), gold (Au), and titanium dioxide (TiO₂).15. The white light emitting device of claim 11, wherein the lightemitting device is configured to emit white light generated bycombination of light from the light emitting diode chip with light fromthe first phosphor and light from the second phosphor, the white lighthaving a color rendering index (CRI) of 85 or higher.
 16. The whitelight emitting device of claim 11, wherein 40% or more of an opticalspectrum of the white light being distributed in a wavelength range of500 nm to 600 nm.
 17. The white light emitting device of claim 11,wherein the wavelength converter includes a first wavelength converterand a second wavelength converter and the second wavelength convertercovers the first wavelength converter.
 18. The white light emittingdevice of claim 17, wherein the second wavelength converter is formed ofmaterial having a different hardness of the first wavelength converter.19. The white light emitting device of claim 11, further comprising: abuffer portion disposed between the wavelength converter and the lightemitting diode chip, wherein the buffer portion has lower hardness thanthe wavelength converter.
 20. The white light emitting device of claim13, wherein the housing further comprises a barrier reflector coveringthe reflector.